The present invention relates to a technique of forming a liquid hydrocarbon fuel from coal, particularly, to a method of estimating the effluent amounts of each of gaseous phase and liquid phase reaction products at the outlet of each bubbling tower (reaction vessel) of a multi-stage bubbling tower liquefying reactor using various kinds of coals as the raw material, said liquefying reactor being optionally scaled up by using an electronic computer.
Concerning the process for forming a hydrocarbon fuel directly from coal, various processes have been developed as a direct coal liquefying process including an IG process (The Chemistry and Technology of Coal. J.G. Speight, marceldekker, Inc. 1994, NEDOL process, Japan Coal Oil K.K. catalog). In each of these processes, in which coal is subjected to a hydrogenation cracking under a high temperature and a high pressure, a finely pulverized coal is dispersed in a hydrocarbon solvent to form a slurry and the resultant slurry is supplied to a reactor of a high temperature and a high pressure. In general, a slurry pre-heater is arranged in the front stage of the reactor for heating the coal slurry of room temperature to a temperature close to the reaction temperature in a relatively short time.
The coal liquefying reaction in the NEDOL process is a gas-liquid-solid heterogeneous phase reaction, in which a hydrogen gas is blown under a high temperature of about 450xc2x0 C. and a high pressure of about 170 kg/cm2 into a slurry consisting of the coal, a solvent and a catalyst so as to subject the coal to the hydrogenation cracking to form a liquid hydrocarbon. The type of the reactor is a completely mixed vessel column reactor consisting of at least three bubbling towers (reaction vessels) connected in series even in the pilot plant scale, in which the hydrogenation cracking proceeds in the bubbling tower reactor on the downstream side to make the molecular weight of the resultant hydrocarbon lower toward the bubbling tower reactor on the downstream side.
A most portion of the low molecular weight hydrocarbon having a low boiling point such as benzene, toluene and phenols is estimated to be present in the gaseous phase even under the high temperature and high pressure because of the gas-liquid equilibrium, with the result that the amount of the liquid phase component having a low boiling point is relatively decreased. Also, the liquefied oil having a low and intermediate boiling points is estimated to be present partly in the gaseous phase. As a result, the flow rate of the liquid phase within the bubbling tower reactor is decreased, and the residence time of the liquid phase tends to be increased with progress toward the bubbling tower reactor on the downstream side. In the extreme case, the liquid phase is developed into a coking trouble.
As described above, the gas-liquid equilibrium inherent in the series-connected multi-stage bubbling tower liquefying reactor is formed by the process conditions of each bubbling tower reactor, i.e., the reaction temperature, the reaction pressure, the composition of the liquid hydrocarbon flowing into the bubbling tower reactor, and the hydrogen gas amount. Also, the reactor is featured in that the reactor has its own residence time of the liquid phase, i.e., the reaction time, and the total reaction time is equal to the sum of the liquid phase residence time in each of the bubbling tower reactors.
The inorganic gas, hydrocarbon gas and the liquefied oil are present both in the gaseous phase and the liquid phase within the liquefying reaction tower. However, the ratio of the gaseous phase to the liquid phase within the reaction tower relates to the gas-liquid equilibrium under high temperatures and high pressures. It is difficult and highly troublesome to calculate the gas-liquid equilibrium of this kind and, thus, the equilibrium has scarcely been studied to date.
Under the circumstances, in the design of the series-connected multi-stage bubbling tower coal liquefying reactor, it was customary in the past to multiply the supply volume rate of the coal slurry under room temperature and atmospheric pressure by the apparent residence time on the assumption that the liquefying reaction is a liquid phase homogeneous reaction so as to obtain a reaction volume. Also, the volume of a single bubbling tower was obtained by dividing the reaction volume by the number of bubbling towers. It follows that the effluent amount of each component at the outlet of the reactor was estimated on the assumption that the residence time in each tower was equal to each other.
Similarly, where the reaction rate of the coal liquefying reaction is obtained from the experimental data obtained from the series-connected multi-stage bubbling tower coal liquefying reactor, the apparent residence time was obtained from the supply volume rate of the coal slurry under room temperature and atmospheric pressure and the volume of the reaction vessel. Alternatively, the residence time is estimated under assumed conditions, e.g., on the assumption that the liquefying reaction is a liquid phase homogeneous reaction, though the reaction is a heterogeneous reaction between a gaseous phase and a liquid phase, so as to obtain an analytical value under the assumed conditions and, thus, to estimate the reaction rate of each component of the reaction products (Reaction Engineering by Kenji Hashimoto, Baifukan Publishing Co., 1993).
In general, where the forming amount of the reaction product is estimated or where, by contraries, the reaction rate constant is obtained from the forming amount, some reaction model is set first so as to determine the reaction route. Also, the reaction rate formula is established so as to estimate the forming amount and to analyze the reaction rate. In the coal liquefying reaction, however, each of the raw material coal and the reaction product of the liquefied oil is a mixture having a complex composition, making it impossible to describe the reaction by the stoichiometry like the ordinary chemical reaction. Therefore, employed is the technique of classifying the coal or the liquefied oil into small groups each consisting of a mixture of components similar to each other in properties. In this case, the classified small group is handled as if the small group provides a pure substance in the ordinary chemical formula so as to analyze the reaction. Various methods of classifying the coal or the liquefied oil and various reaction models differing from each other in the reaction route have been proposed to date (Coal Conversion Utilization Technology, compiled by Yuzo Sanada, ICP, 1994).
As a general tendency, a complex reaction model, in which the coal or the liquefied oil is finely classified into many groups and various reaction routes are set among these groups, well coincides with the experimental data. However, where the reaction amount is estimated by using the complex model, a very large number of parameters that must be experimentally determined are required, making it difficult to analyze the reaction rate.
In performing the feasibility study of a coal liquefying plant, the size and the number of liquefying reactors are important factors giving a serious influence to the construction cost of the plant. In order to make optimum the size and the number of liquefying reactors, it is necessary to conduct many case studies. To be more specific, it is necessary to estimate the forming amount of each component of the liquefied product under various operating conditions.
In the conventional method of estimating the forming amount that has been employed to date, used is an apparent residence time as already pointed out, making it substantially impossible to deal with the changes in the scale and shape of the reactor and in the number of reaction towers. Needless to say, the changes in the operating conditions such as the reaction temperature and the blowing amount of the hydrogen gas are not reflected at all in the residence time. Naturally, the conventional estimating method was indeed insufficient.
For conducting the feasibility study of a coal liquefying plant, required is an estimating technology, in which the flow rates of the gaseous phase and the liquid phase are estimated in view of the gas-liquid equilibrium within each reaction tower, a true residence time is obtained for each reaction tower based on the estimated flow rates, and the forming amount of the liquefied product can be estimated by using the true residence time thus obtained.
Also, where the forming amount is estimated by using the true residence time, it is also necessary for the reaction rate constant used for the estimation to be a reaction rate constant based on the true residence time. An estimating technology, in which the flow rates of the gaseous phase and the liquid phase are estimated in view of the gas-liquid equilibrium within each reaction tower, a true residence time is obtained for each reaction tower based on the estimated flow rates, and the reaction rate constant of the liquefying reaction can be estimated by using the true residence time thus obtained, is required in also the case where the reaction rate of the coal liquefying reaction is obtained from the experimental data in the series-connected multi-stage bubbling tower coal liquefying reactor.
Where the forming amount of the liquefied product is estimated or the reaction rate constant is calculated by using the true residence time, the technology for terminating the calculation by trial and error is absolutely necessary, because the true residence time itself is a function of the forming amount of the liquefied product. Therefore, in the case of using an excessively complex reaction model, the calculation is unlikely to be terminated by trial and error, making it impossible to carry out the estimation. Particularly, where the reaction rate of the coal liquefying reaction is obtained from the experimental data obtained from the series connected multi-stage bubbling tower coal liquefying reactor, it is very difficult to perform analysis for obtaining parameters such as the reaction rate constant in the case of using a complex reaction model.
On the other hand, if the reaction model is excessively simplified, it is impossible to depict the actual reaction phenomenon. As already described, in the coal liquefying reaction, each of the raw material coal and the reaction product of the liquefied oil is a mixture having complex composition, making it impossible to describe the coal liquefying reaction by the stoichiometry like the ordinary chemical reaction. If the reaction is excessively simplified, it is impossible to depict the difference in the reactivity depending on the kind of the coal and the difference in the forming amount for each component of the liquefied product.
To be more specific, for the estimation using a true residence time, it is required to establish a reaction model having a complexity such that the actual reaction phenomenon can be depicted and, at the same time, a simplicity such that the analysis for obtaining the parameter such as a reaction rate constant is not made troublesome and to determine actually the parameter.
The composition and properties of the coal to be liquefied widely differ from each other depending on the kind, the place of production, or the like of the coal. Therefore, even if a simple reaction model is established such that the analysis for obtaining the parameter such as the reaction rate constant is not made difficult, it is necessary to set up the optimum conditions in actually liquefying the coal based on the reaction model. Specifically, in order to select the reaction temperature, the reaction pressure and the reaction time adapted for the kind of the coal (raw material coal), it is necessary to conduct a continuous demonstrating operation by using a bench scale plant or a pilot plant and to evaluate the yield and the ratios of the components of the obtained hydrocarbon fuel so as to set up the optimum conditions. It follows that a tremendous developing cost and much time are required for each kind of the coal. Under the circumstances, it is strongly required to develop the technology that permits easily selecting the conditions for the liquefying reaction such as the reaction temperature, the reaction pressure and reaction time and also permits easily selecting the reaction rate constant.
An object of the present invention, which has been achieved in view of the requirements described above, is to provide an estimation simulating technology that permits depicting the actual reaction phenomenon and also permits estimating the forming amount of the liquefied product by using a true residence time in the coal liquefying reaction.
The present invention, which has been achieved in view of the requirement described above, is intended to provide the technology that permits easily obtaining the reaction rate constant for each of different kinds of coals without requiring the experiment involving a tremendous developing cost and without requiring the demonstrating operation by using a continuous apparatus.
The object described above has been achieved by developing a method for estimating the effluent amount for each component of the effluent from a coal liquefying reactor formed of a vessel type reactor operated under a high temperature and a high pressure by using an electronic computer based on the residence time in view of the gas-liquid equilibrium, by developing another method for estimating the reaction rate constant of the coal liquefying reaction from the experimental data of the effluent amount for each component of the effluent from the N-th vessel of a vessel column reactor operated under a high temperature and a high pressure and consisting of N-number of vessels based on the residence time in view of the gas-liquid equilibrium, by establishing a reaction model having a complexity such that the actual reaction phenomenon can be depicted and also having a simplicity such that the analysis for obtaining the parameter such as the reaction rate constant is not rendered difficult, and by actually determining the parameter.
Also, the object of the present invention has been achieved by analyzing the rate of the liquefying reaction by using the reaction model so as to obtain a reaction rate constant with respect to a plurality of coals differing from each other in the degree of coalification and by allowing the obtained reaction rate constant to relate to the component of the coal the properties of which can be specified.
According to a first aspect of the present invention, there is provided a method of estimating the effluent amount for each component of the effluent at the outlet of a reaction vessel in which a liquefying reaction is carried out by blowing a hydrogen gas into a coal slurry, comprising the steps of calculating the reaction vessel residence time within the reaction vessel for each of the gaseous phase and the liquid phase by assuming the effluent amount for each component of the effluent; calculating the effluent amount for each component of the effluent on the basis of the reaction vessel residence time, the inflow amount for each component of the influent into the reactor, and a primary irreversible reaction rate formula derived from a predetermined coal liquefying reaction model; and repeating the calculation until the assumed effluent amount for each component coincides within a predetermined range of error with the effluent amount for each component obtained by calculation so as to determine the estimated value of the effluent amount for each component.
According to a second aspect of the present invention, there is provided a method of estimating the effluent amount for each component of the effluent of a coal liquefying reactor formed of a vessel type reactor operated under a high temperature and a high pressure, comprising the steps of assuming the effluent amount for each component of the effluent so as to calculate a gas-liquid equilibrium composition within the reaction vessel of a mixture of the composition; further calculating the volume flow rates of the gaseous phase and the liquid phase within the reaction vessel; calculating the residence time of the gaseous phase and the liquid phase within the reaction vessel on the basis of the gas hold up within the reaction vessel calculated from the volume flow rate and the empirical formula; calculating the effluent amount for each component of the effluent on the basis of a primary irreversible reaction rate formula derived from the residence time within the reaction vessel, the inflow amount for each component of the influent into the reactor, and a specified coal liquefying reaction model; comparing the effluent amount for each component assumed first with the effluent amount for each component obtained by calculation; and repeating the series of calculations until the two effluent amounts for each component are allowed to coincide with each other for each component within a predetermined range of error.
According to a third aspect of the present invention, there is provided a method of estimating a reaction rate constant for a coal liquefying reaction on the basis of the actually measured value of the effluent amount for each component of the N-th vessel of a vessel column reactor consisting of an N-number of vessels and operated under a high temperature and a high pressure, comprising the steps of assuming a reaction rate constant; successively calculating the effluent amount for each component of the effluent from each vessel until the N-th vessel by using the assumed reaction rate constant; comparing the calculated value of the effluent amount for each component of the N-th vessel with the actually measured value; and repeating the series of calculations until these two sets of the effluent amounts for each component are allowed to coincide with each other within a predetermined range of error.
According to a fourth aspect of the present invention, there is provided a method of estimating the reaction rate constant of the coal liquefying reaction on the basis of the actually measured value of the effluent for each component of the N-th vessel of a vessel column reactor consisting of an N-number of vessels and operated under a high temperature and a high pressure, comprising the steps of assuming a reaction rate constant; successively calculating the effluent amount for each component of the effluent from each vessel until the Nxe2x88x921-th vessel by using the assumed reaction rate constant; newly calculating a reaction rate constant on the basis of the effluent amount for each component of the Nxe2x88x921-th vessel and the effluent amount for each component of the N-th vessel; comparing the reaction rate constant assumed first with the reaction rate constant newly obtained by calculation; and repeating the series of calculations until these two sets of reaction rate constants are allowed to coincide with each other for each reaction rate constant within a predetermined range of error.
According to a fifth aspect of the present invention, there is provided a method of estimating the effluent amount for each component of the effluent of a coal liquefying reactor consisting of a bubble tower reactor operated under a high temperature and a high pressure, wherein used is a primary irreversible reaction rate formula derived from a reaction model in which a coal excluding water and ash is classified into three components consisting of a component having a high liquefying reactivity, a component having a low liquefying reactivity and a component highly unlikely to be liquefied; the liquefied oil and the solid liquefied product are classified into four components consisting of a liquefied oil component having a low boiling point, a liquefied oil component having an intermediate boiling point, a liquefied oil component having a high boiling point, and asphaltenes containing the liquefied oil; the other liquefied product is classified into four components consisting of a lower hydrocarbon gas, carbon monoxide and carbon dioxide gases, water, and hydrogen sulfide and ammonia gases; and the coal is decomposed by the reaction among 12 components consisting of the three components of the coal, the four components of the liquefied oil and the solid liquefied products, the four components of the other liquefied product, and hydrogen into a liquefied product along the reaction route in which a consecutive reaction and a parallel reaction of a first order irreversible reaction are combined, and the liquefied product is further decomposed partly into another liquefied product having a smaller molecular weight.
The present invention also provides a method of estimating the reaction rate constant of a coal liquefying reaction on the basis of the actually measured value of the effluent amount for each component of the N-th vessel of a vessel column reactor consisting of an N-number of vessels and operated under a high temperature and a high pressure, wherein used is a primary irreversible reaction rate formula derived from a reaction model in which a coal excluding water and ash is classified into three components consisting of a component having a high liquefying reactivity, a component having a low liquefying reactivity and a component highly unlikely to be liquefied; the liquefied oil and the solid liquefied product are classified into four components consisting of a liquefied oil component having a low boiling point, a liquefied oil component having an intermediate boiling point, a liquefied oil component having a high boiling point, and asphaltenes containing the liquefied oil; the other liquefied product is classified into four components consisting of a lower hydrocarbon gas, carbon monoxide and carbon dioxide gases, water, and hydrogen sulfide and ammonia gases; and the coal is decomposed by the reaction among 12 components consisting of the three components of the coal, the four components of the liquefied oil and the solid liquefied products, the four components of the other liquefied product, and hydrogen into a liquefied product along the reaction route in which a consecutive reaction and a parallel reaction of a primary reversible reaction are combined, and the liquefied product is further decomposed partly into another liquefied product having a smaller molecular weight.
The present invention also provides a method of estimating the effluent amount for each component of the effluent of a coal liquefying reactor consisting of a bubbling tower reactor operated under a high temperature and a high pressure, wherein, when the liquefied oil or the solid liquefied product is classified into four components consisting of a liquefied oil component having a low boiling point, a liquefied oil component having an intermediate boiling point, a liquefied oil component having a high boiling point, and asphaltenes containing the liquefied oil, and when the other liquefied product is classified into four components consisting of a group of a lower hydrocarbon gas, a group consisting of carbon monoxide and carbon dioxide gases, a group consisting of water alone, and another group consisting of hydrogen sulfide and ammonia gases, the hydrocarbon compound group having 1 to 3 carbon atoms is classified as a lower hydrocarbon gas, a liquefied oil having a boiling point not higher than 220xc2x0 C. under atmospheric pressure and excluding the lower hydrocarbon gas is classified as a liquefied oil component having a low boiling point, a liquefied oil having a boiling point not lower than 220xc2x0 C. and lower than 350xc2x0 C. under atmospheric pressure is classified as a liquefied oil component having an intermediate boiling point, a liquefied oil having a boiling point not lower than 350xc2x0 C. and lower than 538xc2x0 C. under atmospheric pressure is classified as a liquefied oil component having a high boiling point, and a liquefied oil having a boiling point not lower than 538xc2x0 C. under atmospheric pressure and a solid component soluble in tetrahydrofuran are classified as asphaltenes.
The present invention also provides a method of estimating the reaction rate constant of a coal liquefying reaction on the basis of the actually measured value of the effluent amount for each component of the N-th vessel of a vessel column reactor consisting of an N-number of vessels and operated under a high temperature and a high pressure, wherein, when the liquefied oil or the solid liquefied product is classified into four components consisting of a liquefied oil component having a low boiling point, a liquefied oil component having an intermediate boiling point, a liquefied oil component having a high boiling point, and asphaltenes containing the liquefied oil, and when the other liquefied product is classified into four components consisting of a group of a lower hydrocarbon gas, a group consisting of carbon monoxide and carbon dioxide gases, a group consisting of water alone, and another group consisting of hydrogen sulfide and ammonia gases, the hydrocarbon compound group having 1 to 3 carbon atoms is classified as a lower hydrocarbon gas, a liquefied oil having a boiling point not higher than 220xc2x0 C. under atmospheric pressure and excluding the lower hydrocarbon gas is classified as a liquefied oil component having a low boiling point, a liquefied oil having a boiling point not lower than 220xc2x0 C. and lower than 350xc2x0 C. under atmospheric pressure is classified as a liquefied oil component having an intermediate boiling point, a liquefied oil having a boiling point not lower than 350xc2x0 C. and lower than 538xc2x0 C. under atmospheric pressure is classified as a liquefied oil component having a high boiling point, and a liquefied oil having a boiling point not lower than 538xc2x0 C. under atmospheric pressure and a solid component soluble in tetrahydrofuran are classified as asphaltenes.
The present invention also provides a method of estimating the effluent amount for each component of the effluent of a coal liquefying reactor formed of a bubbling tower reactor operated under a high temperature and a high pressure, wherein, when the coal excluding the ash component is classified into three components consisting of a component having a high liquefying reactivity, a component having a low liquefying reactivity, and a component highly unlikely to be liquefied, the component of the coal having at least 0.5/min of a primary irreversible reaction rate constant of the conversion reaction from the coal into a liquefied product at 450xc2x0 C. is classified as the component having a high liquefying reactivity, the component of the coal having the primary irreversible reaction constant smaller than 0.5/min and not smaller than 10xe2x88x924/min is classified as the component having a low liquefying reactivity, and the component of the coal having the primary irreversible reaction constant smaller than 10xe2x88x924/min is classified as the component highly unlikely to be liquefied.
The present invention also provides a method of estimating the effluent amount for each component of the effluent at the outlet of a reaction vessel in which a hydrogen gas is blown into a coal slurry for carrying out a liquefying reaction, comprising the steps of assuming the effluent amount for each component of the effluent in accordance with a coal liquefying reaction model set in advance in respect of each of a plurality of kinds of coal slurries differing from each other in the degree of coalification and calculating the residence time in the reaction vessel for each of the gaseous phase and the liquid phase within the reaction vessel; calculating the effluent amount for each component of the effluent on the basis of the residence time in the reaction vessel, the inflow amount for each component of the influent into the reaction vessel, and a primary irreversible reaction rate formula derived from the coal liquefying reaction model; obtaining a reaction rate constant of the primary irreversible reaction rate formula, which permits the calculated effluent amount for each component and the assumed effluent amount for each component to coincide with each other within a predetermined range of error, followed by obtaining a formula showing the relationship between the component of the coal and the reaction rate constant on the basis of the reaction rate constant obtained for each kind of the coal; and applying the formula showing the particular relationship to an optional kind of coal so as to calculate the reaction rate constant, thereby estimating the effluent amount for each component of the effluent on the basis of the coal liquefying reaction model.
Where coal having a different degree of coalification is liquefied, the reaction rate constant for the coal can be easily obtained in the present invention by substituting the component of the coal in the obtained relationship. Therefore, it is unnecessary to carry out a continuous demonstrating operation using a bench scale plant or a pilot plant, which was required in the past for each of different kinds of coals, making it possible to markedly save the expenses and time required for the development of the coal liquefying technology. The present invention makes it possible to select the kinds of the raw material coals and to study the reacting conditions such as the reaction temperature, the reaction pressure and the reaction time, leading to the possibility of making optimum the shape of the reactor (reaction vessel).
Where the coal excluding water and the ash component is classified into three components consisting of a component having a high liquefying reactivity, a component having a low liquefying reactivity, and a component highly unlikely to be liquefied, where the liquefied oil and the solid liquefied product of the effluent is classified into four components consisting of a component having a low boiling point, a component having an intermediate boiling point, a component having a low boiling point, asphaltenes containing a liquefied oil, and where the other liquefied product of the effluent is classified into four components consisting of a group of a lower hydrocarbon gas, a group of carbon monoxide and carbon dioxide gases, a group consisting of water alone, and a group consisting of hydrogen sulfide and ammonia, the relationship between the reaction rate constant and the component of the coal can be represented as follows:
K32=K320xc3x9710A32{(H/C)xc3x97VM}+B32xe2x80x83xe2x80x83[formula 1]
K43=K430xc3x9710A43{(H/C)xc3x97VM}+B43xe2x80x83xe2x80x83[formula 2]
K54=K540xc3x9710A54{(H/C)xc3x97VM}+B54xe2x80x83xe2x80x83[formula 3]
K63=K630xc3x9710A63{(H/C)xc3x97VM}+B63xe2x80x83xe2x80x83[formula 4]
xe2x80x83K73=K730xc3x9710A73{(H/C)xc3x97VMxe2x88x92O}+B73xe2x80x83xe2x80x83[formula 5]
K103=K1030xc3x9710A103{(H/C)xc3x97O}+B103xe2x80x83xe2x80x83[formula 6]
K93=K930xc3x9710A93{N+S}+B93xe2x80x83xe2x80x83[formula 7]
K81=K810xc3x9710A81{(H/C)xc3x97O}+B91xe2x80x83xe2x80x83[formula 8]
K10=K100xc3x9710A10{(H/C)xc3x97VM}+B10xe2x80x83xe2x80x83[formula 9]
where, K32 is a reaction rate constant of the reaction for producing the asphaltenes from the component of the coal having a low liquefying reactivity;
K43 is a reaction rate constant of the reaction for producing the liquefied oil component having a high boiling point from the asphaltenes;
K54 is a reaction rate constant of the reaction for producing the liquefied oil component having an intermediate boiling point from the liquefied oil component having a high boiling point;
K63 is a reaction rate constant of the reaction for producing the liquefied oil component having a low boiling point from the asphaltenes;
K73 is a reaction rate constant of the reaction for producing the lower hydrocarbon gas from the asphaltenes;
K103 is a reaction rate constant of the reaction for producing the water from the asphaltenes;
K93 is a reaction rate constant of the reaction for producing the hydrogen sulfide and ammonia from the asphaltenes;
K81 is a reaction rate constant of the reaction for producing the hydrogen monoxide gas and the hydrogen dioxide gas from the component of the coal having a high liquefying reactivity; and
K10 is a reaction rate constant of the reaction between the hydrogen gas and the asphaltenes,
where H/C represents the ratio of the hydrogen atom to the carbon atom contained in the dry coal;
O represents the weight ratio of oxygen contained in the dry coal;
N represent the weight ratio of nitrogen contained in the dry coal;
S represents the weight ratio of sulfur contained in the dry coal; and
VM represents the weight ratio of the volatile component contained in the dry coal, and
where A32 represents the inclination of the straight line represented by formula (1), covering the case where (H/C)xc3x97VM is plotted on the abscissa and K32 is plotted on the logarithmic scale on the ordinate;
K320 represents a part of the intercept of the straight line crossing the ordinate, which denotes the value of K32 at (H/C)xc3x97VM of the predetermined kind of coal used for obtaining the relationship noted above;
B32 represents a part of the intercept of the straight line noted above, which denotes a value equal to xe2x88x92A32{(H/C)xc3x97VM} in the case where K32=K320;
A43 represents the inclination of the straight line represented by formula (2), covering the case where (H/C)xc3x97VM is plotted on the abscissa and K43 in a logarithmic scale is plotted on the ordinate;
K430 is a part of the intercept of the straight line crossing the ordinate, which denotes the value of K43 at (H/C)xc3x97VM of the predetermined kind of coal used for obtaining the particular relationship;
B43 represents a part of the intercept of the straight line, which denotes the value equal to xe2x88x92A43{(H/C)xc3x97VM} when K43=K430;
A54 represents the inclination of the straight line represented by formula (3), covering the case where (H/C)xc3x97VM is plotted on the abscissa and K54 is plotted in a logarithmic scale on the ordinate;
K540 represents a part of the intercept of the straight line crossing the ordinate, which denotes the value of K54 at (H/C)xc3x97VM of the predetermined kind of the coal used for obtaining the relationship;
B54 represents a part of the intercept of the straight line, which denotes a value equal to xe2x88x92A54{(H/C)xc3x97VM} when K54=K540;
A63 represents the inclination of the straight line represented by formula (4), covering the case where (H/C)xc3x97VM is plotted on the abscissa and K63 is plotted in a logarithmic scale on the ordinate;
K630 represents a part of the intercept of the straight line crossing the ordinate, which denotes the value of K63 at (H/C)xc3x97VM of the predetermined kind of the coal used for obtaining the relationship;
B63 represents a part of the intercept of the straight line, which denotes a value equal to xe2x88x92A63{(H/C)xc3x97VM} when K63=K630;
A73 represents the inclination of the straight line represented by formula (5), covering the case where (H/C)xc3x97VM is plotted on the abscissa and K73 is plotted in a logarithmic scale on the ordinate;
K730 represents a part of the intercept of the straight line crossing the ordinate, which denotes the value of K73 at (H/C)xc3x97VM of the predetermined kind of the coal used for obtaining the relationship;
B73 represents a part of the intercept of the straight line, which denotes a value equal to xe2x88x92A73{(H/C)xc3x97(VMxe2x88x92O)} when K73=K730;
A103 represents the inclination of the straight line represented by formula (6), covering the case where (H/C)xc3x97O is plotted on the abscissa and K103 is plotted in a logarithmic scale on the ordinate;
K1030 represents a part of the intercept of the straight line crossing the ordinate, which denotes the value of K103 at (H/C)xc3x97O of the predetermined kind of the coal used for obtaining the relationship;
B103 represents a part of the intercept of the straight line, which denotes a value equal to xe2x88x92A103{(H/C)xc3x97O} when K103=K1030;
A93 represents the inclination of the straight line represented by formula (7), covering the case where (N+S) is plotted on the abscissa and K93 is plotted in a logarithmic scale on the ordinate;
K930 represents a part of the intercept of the straight line crossing the ordinate, which denotes the value of K93 at (N+S) of the predetermined kind of the coal used for obtaining the relationship;
B93 represents a part of the intercept of the straight line, which denotes a value equal to xe2x88x92A93(N+S)xc3x97VM} when K93=K930;
A81 represents the inclination of the straight line represented by formula (8), covering the case where (H/C)xc3x97O is plotted on the abscissa and K81 is plotted in a logarithmic scale on the ordinate;
K810 represents a part of the intercept of the straight line crossing the ordinate, which denotes the value of K81 at (H/C)xc3x97O of the predetermined kind of the coal used for obtaining the relationship;
B81 represents a part of the intercept of the straight line, which denotes a value equal to xe2x88x92A81{(H/C)xc3x97O} when K81=K810;
A10 represents the inclination of the straight line represented by formula (9), covering the case where (H/C)xc3x97VM is plotted on the abscissa and K10 is plotted in a logarithmic scale on the ordinate;
K100 represents a part of the intercept of the straight line crossing the ordinate, which denotes the value of K10 at (H/C)xc3x97VM of the predetermined kind of the coal used for obtaining the relationship; and
B10 represents a part of the intercept of the straight line, which denotes a value equal to xe2x88x92A10{(H/C)xc3x97VM} when K10=K100.